function F = function_F2(X)
    % 输入归一化到[0,1]^2，映射到Franke的[0,3]^2定义域
    x = 3 * X(:,1);
    y = 3 * X(:,2);
    
    % 计算四项
    term1 = 0.75 * exp(-((x-2).^2 + (y-2).^2)/4);
    term2 = 0.75 * exp(-(x+3).^2/18 - (y+3).^2/2);
    term3 = 0.5 * exp(-(x-7).^2/2 - (y-3).^2/2);
    term4 = -0.2 * exp(-(x-4).^2 - (y-4).^2);
    
    F = term1 + term2 + term3 + term4;
end
